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Mixing synthetic oil and real oil?

Discussion in 'The Garage' started by divorced, Dec 27, 2004.

  1. divorced

    divorced 3/4 ton status

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    A few weeks ago I bought a 1972 C10 with a rebuilt 350 and there is an oil change sticker on the windsheild that says they used synthetic oil. I have no desire to use synthetic oil; I want to use regular oil. Can the two be mixed? How do I make the change?
     
  2. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    I wouldn't mix the oils, I have heard it can cause foaming. Converting is easy.....just drain out the synthetic, change the filter, and add the desired oil.

    On another note if the engine does not burn or leak with synthetic I would definantly run it.
     
  3. divorced

    divorced 3/4 ton status

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    Thanks. I wasn't sure if it was as simple as just changing the oil or if it needed changed a few times quickly to "flush" it out.

    I know on semi trucks I have been told that it is not good to run regular oil in a transmission or rear end that had synthetic, but I didn't know if little trucks are as picky.
     
  4. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    Well I should have asked how many miles are on the engine. You could change the oil and run it for a few minutes with a pint of diesel mixed in the oil to be safe but I don't think it is all that big of a deal going from a synthetic back to dyno oil. It's going from conventional oil to synthetic on an engine that can be tricky. IIRC of course. I went from conv. oil after breaking in my 406 to mobile 1 syn. but after springing leaks I went back to conventional.
     
  5. BAJA_BLAZER

    BAJA_BLAZER 1/2 ton status Author

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    It’s not Rocket Science.

    Several companies offer Synthetic/Mineral Oil blends, so there is nothing wrong with mixing them. Just like there is nothing “wrong” with mixing brands or viscosities. No more so than drinking a Coors after polishing off all the Bud.

    From the Castrol Website:

    “Synthetics are sometimes mixed with conventional mineral oils to produce a cost-effective middle ground between the two, referred to as a "semi or part-synthetic" However, while semi or part-synthetics and conventional mineral oils are both capable lubricants, there is no contest as to which type of oil does the best job. For the highest level of engine protection, fully synthetic lubricants come out on top every time.”
     
  6. divorced

    divorced 3/4 ton status

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    That clears it up alot, thanks! :D
     
  7. diesel4me

    diesel4me 1 ton status Premium Member

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    read the can

    I have heard from factory reps that if the oil has a military spec number on the can,it is misceble with all other oils--this is a requirement for any oil sold to the U.S. government for military use--they dont want an engine seizing up when oil is added to whatever is in the vehicle already--when your in combat,and the oil is low,you dont have time to see if its conventional,or synthetic,or compatible with whatever is already in the engine I guess!:crazy:

    I'd say run the synthetic if its not leaking or burning any oil--it costs more,but offers much better protection than regular "dead dinosour" oil...I doubt if switching back to regular would have any ill effects though--I've seen more trouble when going from regular to synthetic,the synthetic oil loosens up more crud and leaks easier than regular oil does..the engine will start easier in the cold and get oiled up quicker in the winter with synthetic oil,and does not turn to sludge in the heat of summer as easily as regular oil....:crazy:
     

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